What about an anime based off of one of the most popular games of all time: Tetris? A romantic story of Block-chan trying to make Line-senpai notice her, which will most likely never happen since he never shows up.

Excuuuuuuuuuuze me, princess!!! But Zelda already HAD an adaptation. And its memorable today, trust me. "By the way princess, you think that deserves a kiss?"

Um... Square already demonstrated years ago why FF doesn't get anime adaptations: Final Fantasy: Legend of the Crystals OVA, and Final Fantasy Unlimited... Or do people forget about that abomination?
(The there's the horrible attempt at Second Story with Star Ocean EX.... The series was soo bad that the director wasn't even allowed to finish the series with money out of his own pocket.)

Kingdom Hearts? First Disney won't let it happen, and KH stopped being interesting once it left the PS2 platform. (There were only 2 games worth playing. Now the franchise is so confusing that I'm having troubles with "it's for kids"! If I don't get it how would the 5 year old it's intended for?

Why do games need adaptations anyways?
(Then again, you might sell me on a Sexy Beach anime...hentai Or Artificial Academy?...

lol Disney was going to make a KH cartoon, but it was scrapped, so your "Disney won't let it happen" is wrong. The story of Kingdom Hearts is not for kids, said by the creator, Tetsuya Nomura, himself. KH1, KH2, and Birth by Sleep, originally going to be on PS2, but Re:COM delayed it. Formerly known as Episode 0/KH0, but is now 0.1 due to X[Chi](the new 0) is another KH game worth playing. All the games are important even if you don't want to play them.

I always thought Odin Sphere would make a perfect anime. It had incredibly detailed anime-styled graphics and a genuinely EPIC plot- one of the best I've ever played through. It's getting an updated Vita remake, and that's almost enough to convince me to go out and get a Vita, even though I already 100%ed the game on PS2.

which is pretty rational. there's no telling how the adaptation will touch (or butcher) on the story (or which one it will follow), as well as the small viewers demographic, cour limitations, etc. better not let it happen than having it exist only to crash and burn